Kimio Shibayama

Prussian‐blue‐modified electrodes: An application for a stable electrochromic display device

An electrochromic display based on a Prussian‐blue‐modified electrode is described. Prussian blues are deposited electrochemically in a solution of ferric‐ferricyanide. Current flow at +0.2 and +1.0 V is due to the reduction of Fe3+ and the oxidation of Fe2+ in the Prussian‐blue coating, respectively. The result is a display that switches from clear to blue, has high stability, and has a response of less than 100 ms.

Propagation and Amplification of Rayleigh Waves and Piezoelectric Leaky Surface Waves in LiNbO3

Velocities and attenuations of piezoelectric leaky surface waves in LiNbO3 are analyzed. As a result, we have found that the effective electromechanical coupling coefficient of the leaky surface wave propagating along the X axis of a 64° rotated Y‐cut plane is very large, K2 = 0.113, and the attenuation of this wave, caused by radiation of the energy into the solid, is 0.036 dB/wavelength for a free surface and goes to zero for a metalized surface. Moreover, K2 of the elastic surface wave for a 130° rotated Y‐cut, X propagation, is found to be larger than that for a Y cut, Z propagation. The theory is verified experimentally. The theoretical analysis and experiments on amplification are performed for these types of waves. In an experiment utilizing the leaky surface wave, net terminal gain of 13 dB/cm is observed for the interaction between the carrier in 200‐Ω cm Si wafer (0.3×3×10 mm), separately mounted on a LiNbO3 surface, and the leaky surface wave. The air gap between the Si wafer and LiNbO3 single ...

Optimum cut for rotated Y-cut LiNbO 3 crystal used as the substrate of acoustic-surface-wave filters

The existence of a new suppression cut to the most obstructive spurious component consisting of the slower shear wave propagatating in a crystal has been experimentally found out for acousticsurface-wave propagation on LiNbO3. The plate is a 127.86° rotated Y-cut X-propagating plate and has a large electromechanical coupling coefficient.

Third‐order elastic constants of lithium niobate

The third‐order elastic constants of lithium niobate have been measured by small‐amplitude ultrasonic waves as a function of applied stress, including the piezoelectric effects.

PIEZOELECTRIC LEAKY SURFACE WAVE IN LiNbO3

Velocities and attenuations of piezoelectric leaky surface waves in LiNbO3 are computed. As the result, we have found that the effective electromechanical coupling coefficient of the leaky surface wave propagating along the x axis of the 64° rotated y‐cut plane is very large, K2=0.113; and by radiating the energy into the solid this wave attenuation is 0.36 dB/wave‐length for the free surface and goes to zero for the metalized surface.

TE‐TM mode conversion by interaction between elastic surface waves and a laser beam on a metal‐diffused optical waveguide

TEm‐TMn mode conversion by electro‐optic and acousto‐optic effects in a metal‐diffused optical waveguide is described theoretically. Elastic surface waves and laser beams propagate along the X axis on Y‐cut LiNbO3 single crystals, i.e., interactions are collinear. We predict completely the TE1‐TM1 mode conversion at an elastic surface wave power of 33 mW along an interaction length of 5 mm with a width of 1 mm.

An Analysis of an Equivalent Circuit Model for an Interdigital Surface-Acoustic-Wave Transducer

This paper presents a new and simplified equivalent circuit model for an IDT. The model developed here provides more accuracy than the well-known crossed field Smith-model, since it contains the energy storage effect in addition to usual secondary effects. By applying the image parameter theory to the new model, the admittance matrix Yij of the equivalent three-port model for an N-pair IDT has been derived in concise closed form. As an application, the relations of the radiation conductances to metallization ratios for an IDT are investigated.

Thickness dependence of acousto−optic diffraction efficiency in ZnO−film optical waveguides

The thickness dependence of the efficiency of the Bragg diffraction between the same optical modes (TE0→TE0, TM0→TM0) by acoustic surface waves in ZnO−film optical waveguides is investigated at an acoustic frequency of 130 MHz and a film thickness from 0.6 to 8.0 μm. It is observed that the efficiencies for both the TE0 and the TM0 modes vary more than 2 orders of magnitude with the film thickness.

Control of nonlinear effects in acoustic surface waves

Theoretical and experimental investigations are made of nonlinear effects in acoustic surface waves with and without velocity dispersion. First, the results of the investigation of nonlinear effects in surface‐wave devices are reported. Second, it is shown that the nonlinear effects in acoustic surface waves can be controlled by velocity dispersion; namely, when the velocity dispersion of acoustic surface waves is increased, the nonlinear effects are reduced, and when the acoustic surface waves are free from velocity dispersion, the nonlinear effects are increased. The experiment was conducted with specimens of a 131°‐rotated Y‐cut X‐propagating LiNbO3, and the fundamental frequency was about 300 MHz.

Hydrothermal Growth and Characterization of ZnO Single Crystals

Large flawless crystals of ZnO up to 25×10×5 mm3 in size have been grown hydrothermally in a specially designed autoclave. Difficulties on the hydrothermal growth of ZnO single crystals were almost surmouted by in situ determination of solution temperatures under operating conditions. The characteristics of the growth crystals are discussed on the basis of the correlation with growth conditions, and it is found that a nonstoichiometry in the grown ZnO is enhanced with being apt to involve O vacancies due to a reductive atomosphere under hydrothermal conditions and also is related to their some properties.